The overall goal of this research is to inhibit arterial restenosis by promoting better re-endothelialization of an arterial segment after angioplasty. The authors have obtained evidence that TNF is expressed at sites of balloon injury in vivo, and can inhibit endothelial proliferation in vitro. This TNF inhibition appears to work via a repression of the cell cycle regulatory factors E2F1 and cyclin A. They hypothesize that the in vivo expression of TNF is a major factor leading to delayed endothelial regrowth in the injured artery, and thereby promoting intimal thickening as a major part of the restenosis process. By extension, they have preliminary data indicating that E2F1 over expression in the artery wall can accelerate re-endothelialization and thereby inhibit restenosis. The resultant specific aims are therefore as follows: Investigate the role of E2F1 in re-endothelialization and restenosis after balloon angioplasty. They propose to characterize the effect of local over-expression of E2F1 (using adenoviral delivery) on re-endothelialization in the rat carotid injury model. These studies will then be complemented by an analysis of a newly developed mouse carotid artery injury model, using the E2F1 deficient mouse; both in the absence of E2F1, and after adding back E2F1 via adenoviral gene transfer. Investigate certain mechanisms involved in the inhibition of endothelial cell proliferation after balloon angioplasty. Here they plan to determine the molecular mechanisms relevant to TNF-induced inhibition of endothelial proliferation via the repression of E2F1 mRNA and protein expression, with the subsequent down regulation of cyclin A activity. Thus, with respect to the E2F1 gene, they will identify the cis-acting DNA sequences that regulate TNF mediated changes in E2F1 expression in endothelial cells, and characterize the trans-acting factors that bind to these elements. They will also determine the cis elements responsible for TNF-induced repression of cyclin A gene expression and similarly identify relevant trans-acting factors binding to these elements. Investigate the role of cyclin A in restoring proliferation of endothelial cells exposed to TNF. Additional data indicate that cyclin A over-expression alone is sufficient to overcome TNF-mediated endothelial cell growth arrest. They will therefore determine if cyclin A is capable of exerting independent proliferation and survival effects on TNF exposed endothelial cells by over-expressing cyclin A using a tetracycline-responsive inducible gene expression system.
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